As a functional polymer membrane, an ion exchange membrane, a reverse osmosis membrane, a forward osmosis membrane, a gas separation membrane and the like are known as membranes having various kinds of functions.
For example, the ion exchange membrane is used in electrodeionization (EDI), continuous electrodeionization (CEDI), electrodialysis (ED), electrodialysis reversal (EDR) and the like.
The electrodeionization (EDI) is a water treatment process wherein ions are removed from aqueous liquids using an ion exchange membrane and an electrical potential to effect ion transport. It differs from other water purification technologies, such as conventional ion exchange, in that it is does not require the use of chemicals such as acids or caustic soda. EDI can be used to produce ultra pure water. The electrodialysis (ED) and the electrodialysis reversal (EDR) are electrochemical separation processes that remove ions and the like from water and other fluids.
In the ion exchange membrane, study on improvement in membrane resistance has been conducted (for example, see Patent Literature 1 to 3). In the electrodeionization (EDI), the electrodialysis (ED) and the electrodialysis reversal (EDR), deionized water in which ions and so forth are removed from water and other fluids, and concentrated water of removed ions are produced. Thus, a concentration of a fluid in contact with the ion exchange membrane changes in the separation process. Therefore, further improvement in performance has been required as the functional polymer membrane during contact with the fluid having the concentration in a wide range. Moreover, improvement in characteristics of the functional polymer membrane other than the ion exchange membrane has also been demanded.